The electrofluorochrome CC-6 (3,3'-dihexyl 2,2' oxacarbocyanine) has been shown to fluoresce in the presence of glycerol extracted rabbit psoas muscle. The magnitude of the fluorescence varies with the ionic strength of the bathing medium, and the change closely parallels the change in potential measured with a microelectrode. These studies are to be extended to examine the various states of muscle, rigor, relaxation and contraction, as well as to ion exchange resins. The ability of various organic cations to depolarize the acetylcholine activated end-plate membrane in the absence of sodium ions has been measured on the frog sartorias muscle with the moving electrode technique. These studies are to be repeated on the acetylcholine sensitive membrane that arises after denervation of the muscle, to see if the sodium channels behave similarly.